1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus equipped with a fusing device for heat fusing developer onto paper serving as a printing medium.
2. Description of Related Art
Patent Document 1 (Japanese Patent Application Publication hei8-6431) is provided as an example of a conventional image forming apparatus equipped with the type of fusing device mentioned above.
In the image forming apparatus disclosed in Patent Document 1, unusual heating is detected inside the fusing device using a thermistor, and the power supply to the heating body is forced off to prevent damage to the fusing device when the temperature of the heating body exceeds a predetermined temperature.
In the example of the conventional image forming apparatus mentioned above, however, because the heating body inside the fusing device is frequently connected to a commercial power source, a power control unit for supplying the power to the heating body is frequently disposed near a commercial power source unit. Accordingly, a control unit controlling the image forming apparatus and the power control unit are separated and connected by a wire material such as a connection cable. Therefore, in the apparatus having the structure described above, in a case where, for example, the connection cable short circuits to a frame ground or the like of the apparatus because of some abnormality, a control signal from the control unit flows in a direction of the ground, causing the power control unit to be unable to turn off. Therefore, the power control unit is not turned off, so that the power is continuously supplied to the heating body from the commercial power source, causing abnormal heating of the heating body while the power control unit remains turned on. The abnormal heating of the heating body causes the problem of abnormal heating of the fusing device, which damages the fusing device.